The invention relates to a method for cooling a component of a motor vehicle, which is thermally coupled with a cooling volume filled with a liquid coolant.
In motor vehicles many components require cooling. The increased used of high-power electronics in motor vehicles, in particular for driving an electric or hybrid vehicle, increasingly requires the cooling of power electronics components. In addition pure electric drives or hybrid drives are currently also used in high-power motor vehicles, which requires supply of current to and control of high-power electric motors in the motor vehicle. When the motor is operated at full load, very high currents flow through numerous components of the power electronics, in particular voltage converters, but also through various open loop or closed loop control elements and/or very high voltages are present at these components, which even in the case of efficient components produces a large amount of waste heat that has to be dissipated. A cooling system for these components therefore has to be configured so as to ensure sufficient cooling also in the case when a maximal power is converted at the component. The same applies to mechanical components, in particular components of the motor in which significantly different thermal loads can occur during driving.
In order to always ensure sufficient cooling, the cooling of the component has to be configured so that a sufficient cooling of the component is available at maximal load. In order to meet this requirement in particular the power electronics for operating high-power electric drives require large-dimensioned cooling systems. In these cooling systems multiple or very high-power pumps are used in order to pump coolant with high flow velocity through regions in which a heat exchange with components that have to be cooled occurs. Hereby the cooling power maximally provided by these cooling systems is rarely used in typical driving situations of the motor vehicle. During operation of a motor vehicle in normal street traffic, most drivers do not use the maximal power of the motor vehicle. Even when this maximal power is used it is typically used in selected situations for a few seconds such as overtaking or accelerating. Even in the case of a sporty driving, in particular on closed racetracks or the like, the full power is not always used by motor vehicle components. As a result in most driving situations the available cooling power is much greater than actually necessary independent of the type of the driving.
This cooling power unnecessarily exceeds that required for most driving situations and as a result the cooling system of a motor vehicle subjects the electric onboard system of a motor vehicle to unnecessary stress and can thus lead to reduced power and in particular to a reduced range of an electrically driven motor vehicle. A possible approach to adjust the cooling power of such a cooling system would be to lower the pump power of the one or multiple pumps in the cooling circuit of the cooling device in situations that only require a low cooling power. This however involves the problem that high-power cooling devices in motor vehicles are typically constructed so as to only reach a maximal efficiency when coolant is pumped through the cooling system with high velocity for example in order to enable turbulent flows in the regions in which a heat exchange with the component occurs. A high heat transfer is hereby in particular required because power components to be cooled oftentimes have a relatively small surface area and a low thermal inertia so that a high heat transfer oftentimes can only be achieved by turbulent and/or fast flowing coolant. In this case a reduction of the cooling power would lead to a slower flowing coolant and with this to a lower efficiency of the cooling device. In case of a low load this would result in a relative inefficient and with this energy-intensive cooling of the component.